This research proposal is a multi-disciplinary and collaborative approach to the investigation of a number of fundamental mechanisms of the immune response and lymphocyte biology. This program focuses on the biochemistry, genetics and functions of the products of the major histocompatibility complex (MHC), the nature of receptors on immunocompetent cells, and the diverse regulatory mechanisms of immune responses. Individual projects representing collaborative efforts among 2 or more investigators and/or laboratories are proposed to investigate: 1) Immunologic properties of MHC antigen containing liposomes; 2) HLA-D region structure and function; 3) Chemistry and structure of T cell and macrophage Ia antigens; 4) Immunochemistry and function of anigen-specific T cell factors; 5) Antigen-specific T cell factors that modulate myeloma cell differentiation; 6) Ia antigen expression on clonally propogated murine macrophages; 7) Immunogenetics and function of the murine complement system; 8) Lactoperoxidase as a specific immunological probe; 9) Altered T cell reactivity induced by specific immune manipulation; 10) Murine antibodies of limited heterogeneity specific for heterologous insulin and proinsulin; and 11) The role of IgG3 in the immune deficiency of CBA/N mice. These projects will be supported by Core Animal Production, Reagent Production and Hybrid Cell Facilities.